Orthopedic implants, such as intramedullary nails are used in fracture fixation. Prior to inserting an intramedullary nail in the canal of a femur, a bore is generally first created. The bore may be created with a reamer, for example. Once the nail is positioned within the canal of the femur, it is generally secured in place by fasteners, such as locking nails or screws. Such fasteners are generally first inserted through a portion of a patient's bone, such as the femur, and then through a fastener receiving aperture located along the length of the nail. Locking features on the fastener itself, on the nail, or other structures such as locking inserts may be used to secure the fastener in the aperture of the nail.
The backing-out of fasteners, such as screws, in implants has been addressed in patent references. U.S. Pat. No. 7,247,157 teaches a ring for securing an interlocking screw in an implant. In one embodiment, there is shown a bone nail having an implant body including at least one bore with a threaded portion and a bone screw which engages the thread when it is threaded into a bone for the fixation of the implant body. The threaded bore of the implant body has an annular groove, the diameter of which is larger than the thread outer diameter, and which receives a ring of a deformable material with an inner diameter which is smaller than the outer diameter of the thread of the bone screw so that the ring extends partially into the bore.